/* LibTomCrypt, modular cryptographic library -- Tom St Denis * * LibTomCrypt is a library that provides various cryptographic * algorithms in a highly modular and flexible manner. * * The library is free for all purposes without any express * guarantee it works. * * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com */#include "tomcrypt.h"/**  @file hmac_init.c  HMAC support, initialize state, Tom St Denis/Dobes Vandermeer */#ifdef LTC_HMAC#define HMAC_BLOCKSIZE hash_descriptor[hash].blocksize/**   Initialize an HMAC context.   @param hmac     The HMAC state    @param hash     The index of the hash you want to use    @param key      The secret key   @param keylen   The length of the secret key (octets)   @return CRYPT_OK if successful*/int hmac_init(hmac_state *hmac, int hash, const unsigned char *key, unsigned long keylen){    unsigned char *buf;    unsigned long hashsize;    unsigned long i, z;    int err;    LTC_ARGCHK(hmac != NULL);    LTC_ARGCHK(key  != NULL);    /* valid hash? */    if ((err = hash_is_valid(hash)) != CRYPT_OK) {        return err;    }    hmac->hash = hash;    hashsize   = hash_descriptor[hash].hashsize;    /* valid key length? */    if (keylen == 0) {        return CRYPT_INVALID_KEYSIZE;    }    /* allocate ram for buf */    buf = XMALLOC(HMAC_BLOCKSIZE);    if (buf == NULL) {       return CRYPT_MEM;    }    /* allocate memory for key */    hmac->key = XMALLOC(HMAC_BLOCKSIZE);    if (hmac->key == NULL) {       XFREE(buf);       return CRYPT_MEM;    }    /* (1) make sure we have a large enough key */    if(keylen > HMAC_BLOCKSIZE) {        z = HMAC_BLOCKSIZE;        if ((err = hash_memory(hash, key, keylen, hmac->key, &z)) != CRYPT_OK) {           goto LBL_ERR;        }        if(hashsize < HMAC_BLOCKSIZE) {            zeromem((hmac->key) + hashsize, (size_t)(HMAC_BLOCKSIZE - hashsize));        }        keylen = hashsize;    } else {        XMEMCPY(hmac->key, key, (size_t)keylen);        if(keylen < HMAC_BLOCKSIZE) {            zeromem((hmac->key) + keylen, (size_t)(HMAC_BLOCKSIZE - keylen));        }    }    /* Create the initial vector for step (3) */    for(i=0; i < HMAC_BLOCKSIZE;   i++) {       buf[i] = hmac->key[i] ^ 0x36;    }    /* Pre-pend that to the hash data */    if ((err = hash_descriptor[hash].init(&hmac->md)) != CRYPT_OK) {       goto LBL_ERR;    }    if ((err = hash_descriptor[hash].process(&hmac->md, buf, HMAC_BLOCKSIZE)) != CRYPT_OK) {       goto LBL_ERR;    }    goto done;LBL_ERR:    /* free the key since we failed */    XFREE(hmac->key);done:#ifdef LTC_CLEAN_STACK   zeromem(buf, HMAC_BLOCKSIZE);#endif    XFREE(buf);   return err;    }#endif/* $Source: /cvs/libtom/libtomcrypt/src/mac/hmac/hmac_init.c,v $ *//* $Revision: 1.5 $ *//* $Date: 2006/11/03 00:39:49 $ */